A058792 Number of covers of an unlabeled n-set such that every point of the set is covered by exactly 5 subsets of the cover and that intersection of every 5 subsets of the cover contains at most one point.

1, 5, 44, 966, 53535, 7043925, 1775617861, 738134963014, 461550358993886, 409321620633426443, 493892363593918906465

Offset: 1

Author

Vladeta Jovovic, Nov 30 2000

Keywords

• more
• nonn

Comments

Cover may include multiple occurrences of a subset. Also n-rowed binary matrices with distinct rows and all row sums 5.

Links

• Vladeta Jovovic, Formula

Crossrefs

Row n=5 of A331508.

Cf. A050535, A050913, A058783, A058784, A058785.

Extensions

a(7)-a(10) from Andrew Howroyd, Jan 29 2020

a(11) from Sean A. Irvine, Aug 27 2022